1. Technical Field
The present invention generally relates to driver circuits for bistable display devices and control methods thereof and, particularly to a driver circuit for a bistable display device and a control method thereof which can improve the stability of picture optical parameters and image display quality of the bistable display device.
2. Description of the Related Art
Nowadays, applications of slim display devices are becoming more common and bring people's lives with great convenience. An electronic paper display device is a kind of flat panel display device and is regarded as one next-generation display technology due to its advantages of portable and low power consumption.
The electronic paper display device generally has two substrates. A plurality of black particles with positive charges, white particles with negative charges and a solvent are injected between the substrates. One of the substrates is a transparent/translucent substrate, a region of the transparent substrate which is applied with a positive voltage would attract the white particles with negative charges and whereby displays a white state, and another region of the transparent substrate which is applied with a negative voltage would attract the black particles with positive charges and whereby displays a black state. The other substrate has a plurality of common electrodes with a voltage reference formed thereon. The electronic paper (i.e., generally e-paper) display device has bistable characteristic, since the solvent and the charged particles have approximate the same specific gravity, even if the applied electric filed is withdrawn, the charged particles still can be maintained at a fixed position for a considerable period of time until the next electric field is applied. The applied next electric filed would cause the charged particles to move again for displaying another image. Therefore, continuous charging is not needed after updating an image every time and thus low power consumption is achieved.
A driver circuit for the electronic paper display device generally includes a plurality of pixel electrodes, a plurality of high-voltage gate control ports each for providing a first control voltage to control whether to supply one of the pixel electrodes with a high voltage, a plurality of low-voltage gate control port each for providing a second control voltage to control whether to supply one of the pixel electrodes with a low voltage, and a reference potential port for providing a reference potential as a voltage reference for powering the pixel electrodes. When a power supply is stopped, the high-voltage gate control port and the low-voltage gate control port naturally discharge through respective voltage stabilizing capacitor, and thus the discharging speeds are relatively slow; the reference potential port discharges the voltage stabilizing capacitor to the ground through a discharging path controlled by a switch, and thus the discharging speed is relatively fast. However, the above-mentioned situations associated with the relatively slow discharging speeds of the high-voltage gate control port and the low-voltage gate control port and the relatively fast discharging speed of the reference potential port would easily result in the change of picture optical parameters of the bistable display device and therefore the image display quality of the bistable display device is degraded.